[AArch64] Support selecting TPIDR_EL[1-3] as the thread base

[philip.derrin]

Summary

Add an -mtp=el[0-3] option to select which of the AArch64 thread ID registers will be used for the TLS base pointer.

This is a followup to D54685 which added subtarget features to enable accesses to the privileged thread ID registers.

[olista01]

Is there an existing compiler which this option is trying to be compatible with? GCC for AArch64 doesn't currently have an option for this, so we don't have to worry about compatibility with that. If possible, I'd prefer for the option to be "-mtp=", to match the option accepted by clang and GCC for AArch32.

[philip.derrin]

In D59631#1437744, @olista01 wrote:

Is there an existing compiler which this option is trying to be compatible with? GCC for AArch64 doesn't currently have an option for this, so we don't have to worry about compatibility with that. If possible, I'd prefer for the option to be "-mtp=", to match the option accepted by clang and GCC for AArch32.

No, there's no existing option as far as I'm aware.

I'm happy to use -mtp=, as long as it is ok for it to remain in Group<m_arm_Features_Group> and to list values for both AArch32 and AArch64. It looks like these things only affect value completion and documentation; is that correct?

[philip.derrin]

Merged -mtpidr= with existing AArch32 option -mtp=

[olista01]

I can't see any other uses of the option groups, or any way to put an option into two groups, so this LGTM.

I'll commit it for you as before.

include/clang/Driver/Options.td

 def mlong_calls : Flag<["-"], "mlong-calls">, Group<m_Group>,
   HelpText<"Generate branches with extended addressability, usually via indirect jumps.">;
 def mno_long_calls : Flag<["-"], "mno-long-calls">, Group<m_Group>,
   HelpText<"Restore the default behaviour of not generating long calls">;
 def mexecute_only : Flag<["-"], "mexecute-only">, Group<m_arm_Features_Group>,
   HelpText<"Disallow generation of data access to code sections (ARM only)">;
 def mno_execute_only : Flag<["-"], "mno-execute-only">, Group<m_arm_Features_Group>,
   HelpText<"Allow generation of data access to code sections (ARM only)">;
-def mtp_mode_EQ : Joined<["-"], "mtp=">, Group<m_arm_Features_Group>, Values<"soft, cp15">,
-  HelpText<"Read thread pointer from coprocessor register (ARM only)">;
+def mtp_mode_EQ : Joined<["-"], "mtp=">, Group<m_arm_Features_Group>, Values<"soft,cp15,el0,el1,el2,el3">,
+  HelpText<"Thread pointer access method (AArch32/AArch64 only)">;
 def mpure_code : Flag<["-"], "mpure-code">, Alias<mexecute_only>; // Alias for GCC compatibility
 def mno_pure_code : Flag<["-"], "mno-pure-code">, Alias<mno_execute_only>;
 def mtvos_version_min_EQ : Joined<["-"], "mtvos-version-min=">, Group<m_Group>;
 def mappletvos_version_min_EQ : Joined<["-"], "mappletvos-version-min=">, Alias<mtvos_version_min_EQ>;
 def mtvos_simulator_version_min_EQ : Joined<["-"], "mtvos-simulator-version-min=">;
 def mappletvsimulator_version_min_EQ : Joined<["-"], "mappletvsimulator-version-min=">, Alias<mtvos_simulator_version_min_EQ>;
 def mwatchos_version_min_EQ : Joined<["-"], "mwatchos-version-min=">, Group<m_Group>;
 def mwatchos_simulator_version_min_EQ : Joined<["-"], "mwatchos-simulator-version-min=">;

lib/Driver/ToolChains/Arch/AArch64.cpp

if (!success)
     D.Diag(diag::err_drv_clang_unsupported) << A->getAsString(Args);
 
   if (Args.getLastArg(options::OPT_mgeneral_regs_only)) {
     Features.push_back("-fp-armv8");
     Features.push_back("-crypto");
     Features.push_back("-neon");
   }
 
+  if (Arg *A = Args.getLastArg(options::OPT_mtp_mode_EQ)) {
+    StringRef Mtp = A->getValue();
+    if (Mtp == "el3")
+      Features.push_back("+tpidr-el3");
+    else if (Mtp == "el2")
+      Features.push_back("+tpidr-el2");
+    else if (Mtp == "el1")
+      Features.push_back("+tpidr-el1");
+    else if (Mtp != "el0")
+      D.Diag(diag::err_drv_invalid_mtp) << A->getAsString(Args);
+  }
+
   // En/disable crc
   if (Arg *A = Args.getLastArg(options::OPT_mcrc, options::OPT_mnocrc)) {
     if (A->getOption().matches(options::OPT_mcrc))
       Features.push_back("+crc");
     else
       Features.push_back("-crc");
   }
 

test/Driver/clang-translation.c

 // RUN: %clang -target arm-linux -mtp=soft -### -S %s -arch armv7 2>&1 | \
 // RUN: FileCheck -check-prefix=ARMv7_THREAD_POINTER_SOFT %s
 // ARMv7_THREAD_POINTER_SOFT-NOT: "-target-feature" "+read-tp-hard"
 
 // RUN: %clang -target arm-linux -### -S %s -arch armv7 2>&1 | \
 // RUN: FileCheck -check-prefix=ARMv7_THREAD_POINTER_NON %s
 // ARMv7_THREAD_POINTER_NON-NOT: "-target-feature" "+read-tp-hard"
 
+// RUN: %clang -target aarch64-linux -### -S %s -arch armv8a 2>&1 | \
+// RUN: FileCheck -check-prefix=ARMv8_THREAD_POINTER_NON %s
+// ARMv8_THREAD_POINTER_NON-NOT: "-target-feature" "+tpidr-el1"
+// ARMv8_THREAD_POINTER_NON-NOT: "-target-feature" "+tpidr-el2"
+// ARMv8_THREAD_POINTER_NON-NOT: "-target-feature" "+tpidr-el3"
+
+// RUN: %clang -target aarch64-linux -### -S %s -arch armv8a -mtp=el0 2>&1 | \
+// RUN: FileCheck -check-prefix=ARMv8_THREAD_POINTER_EL0 %s
+// ARMv8_THREAD_POINTER_EL0-NOT: "-target-feature" "+tpidr-el1"
+// ARMv8_THREAD_POINTER_EL0-NOT: "-target-feature" "+tpidr-el2"
+// ARMv8_THREAD_POINTER_EL0-NOT: "-target-feature" "+tpidr-el3"
+
+// RUN: %clang -target aarch64-linux -### -S %s -arch armv8a -mtp=el1 2>&1 | \
+// RUN: FileCheck -check-prefix=ARMv8_THREAD_POINTER_EL1 %s
+// ARMv8_THREAD_POINTER_EL1: "-target-feature" "+tpidr-el1"
+// ARMv8_THREAD_POINTER_EL1-NOT: "-target-feature" "+tpidr-el2"
+// ARMv8_THREAD_POINTER_EL1-NOT: "-target-feature" "+tpidr-el3"
+
+// RUN: %clang -target aarch64-linux -### -S %s -arch armv8a -mtp=el2 2>&1 | \
+// RUN: FileCheck -check-prefix=ARMv8_THREAD_POINTER_EL2 %s
+// ARMv8_THREAD_POINTER_EL2-NOT: "-target-feature" "+tpidr-el1"
+// ARMv8_THREAD_POINTER_EL2: "-target-feature" "+tpidr-el2"
+// ARMv8_THREAD_POINTER_EL2-NOT: "-target-feature" "+tpidr-el3"
+
+// RUN: %clang -target aarch64-linux -### -S %s -arch armv8a -mtp=el3 2>&1 | \
+// RUN: FileCheck -check-prefix=ARMv8_THREAD_POINTER_EL3 %s
+// ARMv8_THREAD_POINTER_EL3-NOT: "-target-feature" "+tpidr-el1"
+// ARMv8_THREAD_POINTER_EL3-NOT: "-target-feature" "+tpidr-el2"
+// ARMv8_THREAD_POINTER_EL3: "-target-feature" "+tpidr-el3"
+
 // RUN: %clang -target powerpc64-unknown-linux-gnu \
 // RUN: -### -S %s -mcpu=G5 2>&1 | FileCheck -check-prefix=PPCG5 %s
 // PPCG5: clang
 // PPCG5: "-cc1"
 // PPCG5: "-target-cpu" "g5"
 
 // RUN: %clang -target powerpc64-unknown-linux-gnu \
 // RUN: -### -S %s -mcpu=power7 2>&1 | FileCheck -check-prefix=PPCPWR7 %s